1. Field of the Invention
The invention relates to an exposure device. The invention relates especially to a device for oblique light irradiation which is used for an exposure device or the like in which an alignment layer of a liquid crystal display (LCD) element is irradiated with UV radiation and optical alignment of the liquid crystals is performed.
2. Description of Related Art
To establish the size and the direction of the pre-tilt angle of an optical alignment layer of a liquid crystal display element, a process was proposed in which the liquid crystal display element, as a workpiece, is obliquely irradiated with UV radiation (for example, see FIG. 1 of published Japanese Patent Application HEI 9-211465; U.S. Pat. No. 5,889,571).
The angle of the light incident on the workpiece is different depending on the type of optical alignment layer and the treatment conditions of the other production processes. In a device in which a workpiece is obliquely irradiated with light, and is thus exposed (one such exposure device is called a "device for oblique exposure"), there is a need for free adjustment of the angle of the irradiation light incident in the workpiece.
In the above described device for oblique irradiation, a process for oblique irradiation can be imagined in which a light irradiation part (lamp housing) itself is obliquely angled with respect to the workpiece, as is shown in the above-mentioned figure of published Japanese Patent Application HEI 9-211465.
Furthermore, in published Japanese Patent Application HEI 10-154658 (allowed, commonly owned, co-pending U.S. patent application Ser. No. 09/025,732), a device is shown in which a light irradiation part is provided with an arc-shaped rail and is angled without the lamp itself being tilted.
A light irradiation part (lamp housing) comprises a lamp, a focusing mirror, which focuses the light from the lamp and converts it into parallel light, a collimator and optical elements for deflecting the optical path, such as a reflector or the like.
In the case of the above described light irradiation part in published Japanese Patent Application HEI 10-154658, only a small light irradiation part is needed if the area to be irradiated with light is relatively small. Therefore, a large device for tilting the light irradiation part is not needed either.
Liquid crystal display elements with large substrates of 550.times.650 mm and 650.times.830 mm sizes have recently become more and more common and increasingly important. When the substrate is enlarged, the area to be irradiated accordingly also becomes larger. The light irradiation part is therefore also enlarged.
The weight of the light irradiation part increases when the latter becomes larger; this causes enlargement of the device for angling the light irradiation part and an enormous enlargement of the entire device.